Seismic explosive anchor



July 31, 1962 c. M. JOSLIN SEISMIC EXPLOSIVE ANCHOR Filed April 6, 1959CHARLES M. JOSLIN INVENTOR.

United. States Patent "ice 3,046,886 SEISMIC EXPLOSIVE ANCHOR Charles M.Joslin, Quitman, Miss, assignor, by mesne assignments, to Socony MobilOil Company, Inc., New York, N.Y., a corporation of New York Filed Apr.6, 1959, Ser. No. 804,322 2 Claims. (Cl. 102--21.8)

This invention relates to seismic exploration and more particularly toanchoring explosive charges at selected depths in a shot hole forgenerating seismic waves.

In seismic exploration elongated, tubular containers of explosives areplaced in shot holes and detonated at selected depths for the generationof seismic waves. It is often desirable to utilize a plurality ofseismic charges at different depths in the borehole and to detonate themat predetermined intervals or sequences for enhancing the utility of theresultant seismic waves. Difficulty has been encountered in maintainingcharges at predetermined depths.

It is an object of the present invention to provide a charge anchorwhich is relatively inexpensive and yet which is positive in its actionin maintaining a seismic charge at a given depth as to permit theloading of charges without fouling the electrical circuit leading froman associated detonator or cap to the earths surface.

In accordance with the present invention, there is provided an anchorfor explosive charges, the latter being characterized by a plurality ofcontainers threadedly coupled in an end-to-end array and in which anelongated metallic strap provided with a central aperture receives oneof the mating threaded elements and thus is fitted between adjacentcharge containers. Wings extending from the container in a directionopposite the direction of movement of the charge in a borehole areprovided with tips which resiliently engage the borehole wall and opposemovement of the charge out of the borehole.

In a more specific aspect of the invention, there is provided a seismiccharge array in which a plurality of elongated explosive containers arejoined together in an end-to-end relationship with at least oneelongated strap pierced at the mid-point thereof and secured betweenabutting portions of two adjacent containers and forming arms extendingin diametrically opposed directions and at acute angles relative to theaxis of said array and adapted to engage the walls of a borehole intowhich said array is to be placed and to oppose movement of said arrayout of said borehole.

For a more complete understanding of the present invention and forfurther objects and advantages thereof, reference may now be had to thefollowing description taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a view of a shot anchor blank;

FIG. 2 is a side view of a shot anchor formed from the blank of FIG. 1;

FIG. 3 is a view partially in section showing the shot anchor inposition to be secured to a pair of explosive elements; and

FIG. 4 illustrates a shot anchor in place in a borehole.

Referring now to FIG. 1, there is illustrated a shot anchor comprisingan elongated sheet metal strap which is provided with pointedextremities 11 and 12 and having a central circular aperture 13. Theanchor blank 10 of FIG. 1 is shaped into the form illustrated in FIG. 2.The arms 16 and 17 of the anchor are bent abruptly from a plane of theaperture 13 at an angle of approximately 75 The tips 11 and 12 are bentas along lines 14 and 15, FIG. 1, at an angle which is about 30 from theplane of the arms 16 and 17, respectively.

As illustrated in FIG. 3, the anchor is to be secured between adjacentcontainers of explosives 19 and 20. The

3,046,886 Patented July 31, 1962 arms 16 and 17 extend outwardly fromthe axis of containers 19 and 20. The lower container 19 is providedwith a threaded endmember 21 which is adapted to be threadedly securedinternally of the threaded lower end of the container 20. Suchinterlocking features are provided on commercially available geophysicalexplosives. The apertur 13 is adapted to receive the threaded end member21. When the nut portion of the container 20 is served tightly ontomember 21, the anchor 10 is rigidly secured to and made an integral partof the explosive charge assembly.

An assembly of charges such as illustrated in FIG. 4 includes fourcontainers of explosive 30, 31, 32 and 33 which are interlocked toprovide an elongated charge. Three charge anchors 34, 35 and 36 areincorporated in the assembly rigidly to secure the charge assembly at aselected depth in the borehole. The anchors extend upward and angularlyaway from the axis of the charge assembly as to engage the walls of theborehole 37. Thus the charge unit may be lowered to a preselected depthin the borehole. The loading mechanisms may then be removed without fearof raising the charge unit from the preselected depth.

In operation, a plurality of units such as illustrated in FIG. 4 may beemployed in a single borehole and may be lowered to desired depths andthere anchored.

In accordance with a preferred embodiment of the invention, the chargeanchors were formed of a strip of 14 gauge sheet steel 22" in length and2 A in width. The width of the charge anchor was made equal to thediameter of the charge container for minimum spatial requirements.Charge anchors of 22" in total length were found to be satisfactory foruse in shot holes of the order of four to five inches in diameter.

Having described the invention, it will now be understood that furthermodifications may be made therein without departing from the scope ofthe appended claims. While it has been indicated that metal may be used,it will be understood that other materials of suitable rigidity andcompliance may be employed. Furthermore, the unit may be utilized inconnection with other types of conplings between charge containers. Theaperture 13, receiving one of a pair of telescopically mating elementswhich form the charge coupling structure, permits the anchor to be aunitary element, thus simple in construction but positive in operation.

What is claimed is:

1. In a seismic charge array wherein a plurality of tubular explosivecharge containers are to be connected together in an end-to-end arraywith threadedly mating male and female elements prior to introductioninto a borehole, the combination which comprises an elongated strapincluding a central portion having an aperture adapted to receive one ofsaid male elements, and to be fitted and directly secured between saidtubular containers by the male and female coupling elements with armsextending in diametrically opposed direction from said central portionat an angle of the order of 15 with respect to the walls of saidcontainers, and extending in direction opposite the direction ofmovement of said array into the borehole, each of said arms including anend portion directed outward at an angle of the order of 30 with respectto the plane of its associated arm.

2. A seismic charge array for introduction into a borehole comprising aplurality of elongated explosive containers joined together in anend-to-end relationship, at least one elongated strap pierced at themid-point thereof by said containers and directly secured betweenadjacent containers by end portions of said containers, and forming armsextending in diametrically opposite directions at an angle of the orderof 15 with respect to the axis of said array in directions opposite thedirection of movement 3 of said array in the borehole, and each havingan end portion directed outward at an angle of the order of 30 withrespect to the plane of its associated arm, and adapted to engage thewalls .of the borehole into which said array is to be placed to opposemovement of said 5 array out of the borehole.

References Cited in the file of this patent UNITED STATES PATENTS1,218,140 Weber Mar. 6, 1917 10

